Preparation of alkali metal derivatives of decaborane



July 25, 1961 1.. J. EDWARDS ETAL 2,993,751

PREPARATION OF ALKALI METAL DERIVATIVES 0F DECABORANE Filed March 12, 1956 2 Sheets-Sheet l RUM OF Na B. H

5Q Lil/Q2. v. H

i INVENTORS E2 Ll-I BY July 25, 1961 1.. J. EDWARDS EI'AL 2,993,751

PREPARATION OF ALKALI METAL DERIVATIVES 0F DECABORANE Filed March 12, 1956 2 Sheets-Sheet 2 FIG. 2.

M, W.%M m

2,993,751 PREPARATION OF ALKALI METAL DERIVA- TIVES OF DECABORANE Lawrence J. Edwards, Zelienople, and William V. Hough,

Butler, Pa., assignors to Callery Chemical Company,

Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 12, 1956, Ser. No. 571,038 13 Claims. (Cl. 23-14) This invention relates to new compositions of matter referred to as alkali metal derivatives of decaborane having the general formula MB H where M is an alkali metal such as sodium, postassium or lithium. It also relates to methods for preparing these new compositions of matter and more particularly to a method of preparing the sodium derivative of decaborane having the formula NaB oH g.

The only metal borane salts of the boron hydrides which have been reported in the literature were prepared in 1935 and 1936 by Stock and his co-workers. These included the potassium and sodium salts of diborane, tetraborane, and pentaborane-9. The calcium salt of diborane was also prepared. Since the alkyl derivatives of decaborane have been found to be ideally suited for use as high energy fuels, considerable interest has been aroused in the alkali metal derivatives of decaborane having the general formula MBloHlg as possible intermediates in the preparation of mono-alkyl derivatives of decaborane. We have finally succeeded in preparing these hitherto unkown alkali metal derivatives of decaborane.

It is one object of this invention to provide new compositions of matter referred to herein as alkali metal derivatives of decaborane having the general formula MB H where M is the alkali metal.

A second object is to provide methods of preparing these new alkali metal derivatives of decaborane by the reaction of a basic alkali metal compound with decaborane in an inert organic solvent.

A third object is to provide a method of preparing NaB H by the reaction of sodium hydride, sodium borohydride, sodium trimethoxyborohydride, sodium hydroxide or sodium methoxide with decaborane in an inert solvent consisting of a simple lower alkyl ether, a polyethylene glycol dialkyl ether or hexane.

Other objects will appear from time to time throughout the following description and appended claims.

These new compositions of matter and methods for preparing them will be more fully disclosed hereinafter and the novelty thereof will be particularly pointed out and distinctly claimed.

In the accompanying drawings, there are shown the X-ray pattern and infra-red spectrum for the new compound NaBH13.

This invention is based upon the discovery that when a basic alkali metal compound such as NaH,

NaHB(OCH 3 NaBH NaOH or NaOCH is reacted with decaborane in an inert organic solvent such as diethyl ether at room temperature, one and only one hydrogen of the decaborane molecule is substituted by the alkali metal to form nite Sates Patent 0 an alkali metal derivative of decaborane as shown by the following examples:

Since B H is a protonic acid (normal acid-base titrations with NaOH have been observed) the alkali metal salt of any acid weaker than decaborane will react in a similar manner. Similar reactions take place when the corresponding potassium and lithium compounds are reacted with decaborane. The pressure at which this reaction takes place is not critical. In some cases it is desirable to carry this reaction out under vacuum to facilitate removal and measurement of the hydrogen evolved. The existence of these new alkali metal derivatives of decaborane has been firmly established as shown by the accompanying X-ray pattern and infra-red spectrum of NaB I-I In one experiment, 255.7 mg. of sodium hy'dride of 97% purity, 1910 mg. of decaborane and 3 ml. of diethyl ether were placed in a sealed 150 ml. Pyrex tube at room temperature. The mixture Was agitated in a wrist-action shaker. Evidence of a reaction was visible within 10 minutes by the disappearance of the solid sodium hydride and a color change of the solution from colorless to amber. When the tube Was opened, 1024 millimols of hydrogen were evolved as measured in a Toepler system. The ether was removed by vacuum condensation leaving a pale yellow solid residue. From this solid was sublimed under vacuum 597 mg. of unreacted decaborane. The results confirmed the calculated stoichiometry of one mol of NaH reacting with one mol of B H to yield one mol of hydrogen. The product obtained was a powdered crystalline solid having an elemental analysis corresponding to the empirical formula NaB H This compound is soluble in simple ethers, polyethylene glycol dialkyl ethers and water. The yield of NaB H was quantitative. Further evidence that this empirical formula was correct Was obtained by the reaction of this product with dry HCl in ether from which decaborane and sodium chloride were recovered quantitatively. The infra-red spectrum of NaB H diifered from that of decaborane in that the tentatively assigned B-H--B bridge frequency characteristic of B H was not present. Furthermore, the unique X-ray pattern of NaB H shows that it is a new composition of matter.

In another series of experiments, sodium hydride and decaborane were reacted in diethyl ether and the stoichiometry of the reaction was firmly established to be one mol of hydride to one mol of decaborane which yields one mol of hydrogen and one mol of NaB H as shown in the table below:

Run No.

mmols Ha R6- BIUHH covered 11115. (0211920 charged used Time Temp.

hrs. 0 o.

It is apparent from the data obtained that one and only one hydrogen of the decaborane molecule is replaced by sodium in this reaction regardless of whether an equimolar amount of the starting reactants is used or Whether of transportation and storage. These derivatives are stable and decaborane can be readily regenerated by acidification in non-aqueous solution. These metal derivatives are also potentially useful as intermediates in the preparaan excess of either sodium hydride or decaborane is used. 5 tion of other decaborane derivatives such as alkyl deca- The amount of hydrogen evolved corresponds in every boranes.

case within experimental error to the amount of the start- Having thus described these new compositions of mating reactant not used in excess. A quantitative yield of ter and methods for preparing them, it should be under- NaB H is readily obtained. stood that other variations will become apparent to those Similar reactions were carried out with sodium hy- 10 skilled in the art and that within the scope of the appended droxide and sodium, methoxide respectively with decaclaims, this invention may be practiced otherwise than as borane in either solution. When the hydroxide was used, specifically described. water was formed which was removed from the NaB H What we claim as our invention is: by evacuation. When the methoxide was used, methanol 1. As a new composition of matter, an alkali metal was formed which was readily removed from the 15 derivative of decaborane having the general formula NaB H by similar vacuum techniques. In each case, MB I-I where M is an alkali metal selected from the the X-ray pattern and infra-red spectrum for the product class consisting of sodium, potassium and lithium. corresponded to the product obtained by the reaction of 2. As a new composition of matter, the sodium derivasodium hydroxide with decaborane. It was also found tive of decaborane having the empirical formula NaB H that the hydroxides, methoxides and hydrides of potas- 3. As a new composition of matter, the lithium derivasium and lithium could be substituted for the correspondtive of decaborane having the empirical formula ing sodium compounds with equally effective results to LiB H yield LiB H and KB H Inert solvents such as 4. A method of preparing alkali metal derivatives of hexane and the polyethylene glycol dialkyl ethers may decaborane having the general formula MB H where M also be used for these reactions if desired. is an alkali metal which comprises reacting a strongly In another series of experiments, lithium borohydride basic alkali metal compound with decaborane in a solvent which is ether soluble, was reacted with decaborane in which is inert to the reactants and reaction product at diethyl ether solution at room temperature in a sealed room temperature and atmospheric pressure and recoverpyrex glass tube with continuous agitation. The results ing the MB H formed. obtained are shown below: 5. A method of preparing alkali metal derivatives of mmols mmols mmols mmols mmols mmols Run NO. LlBH BlDHM (021 1920 H2 BzHg (03135320 Charged Charged Charged Recovered Recovered Recovered These results show that one mol of LiBH reacted with decaborane having the general formula MB 'H which one mol of B H to evolve one mol of H one-half mol 40 comprises reacting a strongly basic alkali metal comof B H and that one mol of dietyl ether was absorbed. pound selected from the group consisting of hydrides, Thus, the reaction which occurred can be illustrated as borohydrides, lower alkoxy substituted borohydrides,, hyfollows: droxides, and lower alcoholates of sodium, potassium and (0211920 lithium with decaborane in a solvent which is inert to LlBHl+BmHn- LiBwHia-( i i)2 +0.5BiHa+Ha the reactants and reaction product at room temperature When the LiB H etherate was heated at 100 C., and atmospheric Pressure and recovering the 10 13 all of the ether was evolved leaving solid LiB H e Where M is the alkali metal used- The alkali metal derivatives of decaborane having the A method according to claim 4 in Which the Solvent general f ula MB H where M i th lk li t l, is selected from the class consisting of the lower alkyl give distinctive X-ray patterns and infrared spectra which 50 Simple ethers, Polyethylene glycol dialkyl ethers and difierentiate them from decaborane and establish that hexanethey are decaborane derivatives. These derivatives can 7. A method according to claim 6 in which sodium be converted to a different compound having the genhydride is reacted with decaborane and the reaction proderal empirical formula MB H where M is the alkali uct recovered is NaB H metal, by treatment of an ether solution containing one 5 8- A method according to Claim 6 in which lithium of these compounds with hydrogen at 50 C. and 800 borohydride is reacted with decaborane and the reaction p.s.i.g. pressure. A mild partial hydrolysis of MB H product recovered is LiB H with water results in the evolution of two mols of hydro- 9 A th d according t laim 6 in which the alkali gen P 11101 of derivative Whereas Similar hydrolysis of metal compound and decaborane are reacted in a molar MB H results in the evolution of 2.5 mols of hydrogen ratio of Per mol of denvatlve- 10. A method of preparing the sodium derivative of These new decaborane denvatlve? Wlth the general decaborane having the empirical formula NaB I-I which P M H are if g .1? comprises reacting equimolar quantities of sodium hyactlon i dmiethyl W1 pm Su ur e dried and decaborane in diethyl ether at room temperaand reaction with organic compounds w1ll result in the d h d th reduction of functional groups which are reducible by ture an atmosp pressure an recovermg e decaborane. They also provide a water soluble form of NaBlOHlK formed' decaborane since decaborane itself is insoluble in water. A method of g fe the PP NaBlqHlii These compounds are highly toxic i aqueous l i which comprises reacting equimolar quantities of sodium when taken internally and are useful as insecticides and hydroxide and decaborane in heXaIle at room temperahlm rodenticidese.g., an aqueous solution of NaB H when applied to an anthill results in rapid destruction of the ants. by converting it to the non-volatile NaB H or one of the other alkali metal derivatives herein described for ease The toxicity hazard of decaborane can be reduced and atmospheric pressure and recovering the NaB H formed.

12. A method of preparing the compound NaB H which comprises reacting equimolar quantities of sodium h Xide and decaborane in hexane at room temperature and atmospheric pressure and recovering the NaB 0H13 fOrmed.

13. A method of preparing the compound LiB H which comprises reacting equimolar quantities of lithium borohydride and decaborane in diethyl ether at room temperature and atmospheric pressure to form m ia 2 5) 2 heating said etherate at 50-100 C. to remove the ether and recovering the solid LiB H formed.

References Cited in the file of this patent Schlesinger et al.: J.A.C.S., vol. 75, page 187 (1953).

Stock: Hydrides of Boronand Silicon, pages 85, 13844 0 (1933), Cornell University Press, Ithaca, NY.

Stock et al.: Z. Anorg. Allgem. Chem. vol. 228, pp. 178-192 (1936). I

Sidgwick: Chemical Elements and Their Compounds, vol. 1, pages 346-349 (1950), Oxford Univ. Press, Lon- 10 don. 

1. AS A NEW COMPOSITION OF MATTER, AN ALKALI METAL DERIVATIVE OF DECABORANE HAVING THE GENERAL FORMULA MB10H13 WHERE M IS AN ALKALI METAL SELECTED FROM THE CLASS CONSISTING OF SODIUM, POTASSIUM AND LITHIUM. 